Apparatus for separating liquid from fibrous suspensions

ABSTRACT

The invention relates to an apparatus for separating liquid from solids-liquid mixtures, in particular fibrous matter suspensions, more particularly under pressure, comprising a solid retention component having liquid passages, composed of a screen and a supporting body for the screen. The invention is primarily characterized in that the solids retention component is designed in multiple layers, that layer which faces the solids-liquid mixture taking the form of a screen (3) with apertures (7) and that layer which faces away from the solids-liquid mixture being designed as a support body (4) having slot-shaped apertures (5). The invention furthermore relates to an apparatus according to the present invention in the form of a worm press.

BACKGROUND OF THE INVENTION

The invention relates to an apparatus for separating liquid from fibrousmatter suspensions, comprising a multiple-layered solid retention meanshaving liquid passages, composed of a screen and a supporting body forthe screen, as well as an apparatus in the form of a worm press.

An apparatus of this type is known from DE-C-112321. The press theredescribed serves for pressing liquids from solids, such as pressing ofjuices, water or oil from suitable substances. The solids retentionmeans of that press is of multiple-layered construction and comprises aninner envelope having short slots arranged longitudinally in parallelrows. A woven wire fabric is provided above this envelope, supported byyet a further envelope. In further known apparatus of this kindperforated plates were usually used as a screen. These are usuallyfitted on a support means, the support means comprising countersunkholes into each of which a plurality of the apertures of the screenenter. This involves a great problem in that the perforation spacings ofthe screen and of the support means can virtually not be made to match,as a result of which a major part of the perforations of the screenterminate on the surface of the support means and cannot drain. In theevent of fibrous suspensions, the further problem arises that theperforations of the support means become blocked by the fibres, as aresult of which the dewatering capacity of the apparatus greatlydiminishes. Here to provide a remedy, is one of the objects of theinvention.

SUMMARY OF THE INVENTION

The invention is primarily characterised in that, that layer which facesthe fibrous suspension takes the form of a screen with apertures andthat layer which faces away from the solids-liquid mixture is designedas a support body having slot-shaped apertures and that at least onefree space for liquid distribution is provided between the screen andthe supporting body. The result of this is that the liquid passages ofone layer are not obscured by an adjoining layer which would interferewith the passage of liquid.

According to an advantageous embodiment of the invention, theslot-shaped passages of the supporting body are arranged parallel to oneanother, uniformly distributed over its surface and preferably arrangedin mutually staggered rows.

Preferably according to the invention the cross section of the passagesof the supporting body in downstream direction of the liquid increases.This substantially prevents blocking of the passages by fibres.

Expediently, according to the invention, the free space is provided inthe form of channels between the screen and the supporting body. Theformation of channels between the screen and the supporting bodyactually makes possible effective cleaning from outside. For thatpurpose water is introduced by means of a flat jet nozzle into one ofthe slot-shaped passages, is pressed through the channels and forced outthrough the next slots.

Advantageously, according to the invention, the channels are formed byspacers, in particular battens fitted between the screen and thesupporting body.

According to a further advantageous embodiment of the invention, thechannels are formed by grooves provided in the screen. This permitsreduction of the structural height of the apparatus.

According to an advantageous embodiment of the invention, the channelsare arranged at least essentially transversely in relation to the slotshaped passages of the supporting body. In this manner an optimaldrainage of the liquid is attained, such that with the apparatus a highdewatering capacity is attainable.

In the past a number of passages were obscured by the mounting flanges,whereby the dewatering capacity was reduced.

Advantageously, according to the present invention, channels areprovided in the marginal region of the supporting body in the form ofgrooves provided in the supporting body, extending longitudinally to andas a continuation of the apertures.

According to an advantageous embodiment of the invention, the passagesthrough the screen increase in cross section in the drainage directionof the liquid. In this context it is advantageous if the passages aredirected at right angles to the screen surface.

Advantageously, according to the invention, bores are provided in thescreen serving as passages. According to a funher advantageousembodiment of the invention, slots are provided in the screen serving aspassages.

Expediently, according to the invention, the slot-shaped passages in thesupporting body are provided at right angles to a surface of thesupporting body.

Advantageously, according the invention, the longitudinal direction ofthe slob in the screen is directed at right angles to the longitudinaldirection of the slot-shaped passages through the supporting body.

Advantageously, according to the invention, the inner cross sectionrespectively the aperture width of the passages in the screen and theslot-shaped passages through the supporting body are at least partly inalignment. Such a design is particularly necessary for the functioningof the apparatus according to the invention or for the apparatusaccording to the invention taking the form of a worm press, in theabsence of an interspace between the screen and the supporting body.

According to an advantageous embodiment of the invention, the solidsretention means takes the form of a hollow cylinder or a hollowfrusto-conical body. In that case it may be advantageous if theslot-shaped passages through the supporting body are normal to thegeneratrics of the hollow cylinder or hollow frusto-conical body.Alternatively, it may also be advantageous, if the slot-shaped passagesin the supporting body are orientated approximately in the direction ofthe generatrics of the hollow cylinder or hollow frusto-conical body.

According to an advantageous embodiment of the invention, the passagesthrough the screen enter into grooves of the screen or areinterconnected by grooves, such grooves being provided on the side ofthe screen facing the supporting body, and advantageously extendtransversely to the slot-shaped passages of the supporting body andpreferably approximately in the direction of the generatrics. Thisdesign permits an onward conduction of liquid if a passage through thescreen is provided over a closed region of the supporting body anddirectly bears thereon. The liquid is conducted onwards by grooves onthe surface of the supporting body to the next following slot-shapedpassage through the supporting body and can drain as a result.

According to another advantageous embodiment of the invention, thesolids retention means is of planar design.

The invention also relates to an apparatus according to the presentinvention in the form of a worm press. The apparatus in the form of theworm press is primarily characterised in that the at least one worm ofthe worm press is surrounded by the solids retention means in the formof a hollow cylinder or conical body.

The apparatus according to the invention may be employed advantageously,particularly when dewatering fibrous suspensions introduced into thehousing and subjected to appropriate pressure by the worm.

Advantageously the cylinder wall or conical wall in the worm press,according to the invention, consists of a plurality of parts, inparticular of a plurality of successive cylindrical or conical andfrusto-conical walls.

At the end of the worm, the dewatering can no longer proceed outwardly.For that reason for optimal dewatering in the outlet region of thehollow drum a screen for dewatering inwardly into the cavity isprovided.

Advantageously, according to the invention, the worm of the worm pressis provided on the outer periphery of a hollow drum and the hollow drumin the terminal region of material conveyance in the worm press comprisea cylindrical screen section.

This screen is designed analogously to the screen of the apparatus, ie.it more particularly comprises passages, the cross sections of whichflare towards the interior (in the direction of the axis).

Advantageously the passages of the cylindrical screen section of theworm press have a cross section which increases in the direction ofdraining the liquid in the direction towards the axis of the drum.

In order to provide as large a cross section for the drainage of theliquid, the hollow drum of the worm press is, according to theinvention, in its terminal region, is designed with a conical taper, theconical drum periphery being surrounded by the cylindrical screensection, or where applicable by a solid cylindrical wall followingthereon.

Advantageously and in accordance with the invention, the worm press has,fixed in the terminal region to the solid cylinder wall, preferablytransversely to the longitudinal axis, partition walls which jointlywith the screen cylinder section and, where applicable, the solidcylinder wall and with the drum wall form channels for the discharge ofthe liquid.

Advantageously and in accordance with the invention, the worm presscomprises at the end of the channels an overflow for liquid.

Advantageously and in accordance with the invention, the worm presscomprises at the end of the channels rinsing means, preferably spraynozzles, for cleaning the channels, in particular of entrained fibres.

According to an advantageous embodiment of the worm press, pressuregenerating or regulating means, in particular flaps, are provided forpressure generation or regulation in the solids-liquid mixture in theterminal region outside of the screen cylinder section or solid cylinderwall as the case may be.

In what follows the invention will be explained with reference to thedrawings. There is shown in: FIG. 1 a longitudinal section through anapparatus according to the invention, FIG. 2 an enlarged representationof detail 2 taken from FIG. 1, FIG. 3 a plan view onto the supportmeans, FIG. 3a a plan view onto the support means with the screen therebelow, FIG. 4a a cross sectional segment of a circularly curved devicein the region of a fastening flange, FIG. 4b a modification of FIG. 4a,FIG. 5a a cross section of a screen with bores and grooves, FIG. 5b aplan view on a developed representation of a screen for a circularlycurved apparatus, FIG. 6 a modification of FIG. 4a ,b using spacers forthe channels, FIG. 7 a longitudinal section through a worm pressaccording to the invention, FIG. 8 a longitudinal section in theterminal region of the worm press, and FIG. 9 a cross sectional segmentin the terminal region of the worm press.

BRIEF DESCRIPTION OF THE DRAWING

In the FIGS. 1 denotes the space in which the pressurized fibroussuspension to be dewatered is maintained, 2 the space into which thewater of the fibrous suspension is pressed, 3 the screen required forthe dewatering process, 4 the associated supporting body, 5 the passagesof the supporting body 4, 6 the channels between the screen 3 andsupporting body 4 and 7 the passages through the screen 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 represents an apparatus according to the invention, by means ofwhich from a fibrous suspension to be dewatered, maintained in the space1, with the application of pressure, water is transferred in thedirection of the arrow 8 into the space 2 and is discharged from there.Solids, in particular fibres, are retained on the screen 3, while theliquid, predominantly water, passes through the passages 7. The liquidafter having passed through the passages 7 of the screen 3 becomesdistributed in the channels 6, provided between the screen 3 and thesupporting body 4 and enters through the passages 5 of the supportingbody 4 into the space 2. Due to suitable configurations of the passages5 of the supporting body 4 and of the passages 7 in the screen 3, ie.cross sectional flaring in the downstream direction 8 of the liquid--anyfibres which may have entered into the passages 5, 7 are readily removedby subsequent liquid under pressure and discharged with the liquid fromthe space 2.

FIG. 2 shows an enlarged representation of detail 2 of FIG. 1, wherebythe construction of the apparatus according to the invention is furtherelucidated.

FIG. 3 shows a plan view onto the supporting body 4 taken from thedirection of the space 2, ie. contrary to the direction of flow of theliquid, the configuration of the passages and their arrangement in thesupporting body 4 being apparent. The double outlines of the passages 5are due to the cross sectional change of the passages 5.

FIG. 3a shows a plan view onto the supporting body 4 including thescreen 3 underneath it. It is apparent from this figure how the liquidpasses from the passages 7 in the screen 3 via channel 6 into thepassages 5 of the supporting body 4.

FIG. 4a and FIG. 4b show further advantageous embodiments of anapparatus according to the invention, which is of circular curvature. Aflange required for fitting the apparatus to a housing or for fittingseveral of the apparatus to one another in conventional designs obscuresa series of apertures whereby the dewatering capacity is reduced. Due tothe design in accordance with the invention, it is now possible also forthe liquid in the region of the flange 9 to enter through the passages 7of the screen 3 into the channels 6' in the form of grooves and fromthere through the passages 5 of the supporting member 4 into the space 2(as indicated by arrow 10).

In FIG. 5a an advantageous embodiment of the screen 3 is illustrated,wherein the passages 7 of the screen 3 on that side which faces thesolids-liquid mixture take the form of bores, which on the side of thescreen 3 facing the support body 4 each enter into grooves 6". Theliquid from the solids-liquid mixture passes through passages 7 in thescreen 3 (as indicated by the arrow 10) to the support body (which isnot illustrated). Whenever a passage 7 of the screen 3 is positionedabove a blocked region of the support body 4 and lies directly thereon,the liquid can be passed on through the grooves 6" in the screen 3 alongthe surface of the support body 4 to the next following slot-shapedpassage 5 in the support body 4. In this manner the drainage of liquidthrough the passage 7 of the screen 3 is ensured.

FIG. 5b shows a plan view onto a developed representation of a screen 3for a circularly curved apparatus for the separation of liquid fromsolids-liquid mixtures. The passages 7 which comprise grooves 6" areequi-distantly arranged in a row, the passages 7 in adjoining rows beingmutually staggered by half the distance of the passages 7.

In FIG. 6 an advantageous embodiment of the channels 6 including spacers6a, is illustrated. This is particularly expedient where large volumesof water arise or with special materials to be dewatered.

A worm press according to the present invention is illustrated in FIG.7. The fibrous suspension to be dewatered is introduced by way of thefeed nipple 11 into the worm chamber. This chamber is composed of aplurality of successive circularly curved screens 3 and supportingbodies 4 forming the cylinder wall. The worm 14 is in this contextfitted on a hollow drum 13. At the ends of the drum 13 roller axial pins15 are fitted by way of which the drum 13 (including the worm 14) ispivotally mounted in bearings 16. The material to be dewatered issubsequently discharged through a chum 12 from the worm press. The drum13 comprises in the terminal region of the worm press a conicallytapering drum wall 17. The drum wall 17, the partitions 19 and the solidcylinder wall 22 or where applicable the screen cylinder section 3'jointly form channels 23 for the discharge of the liquid. Finally, theliquid is discharged by way of an overflow 18 from the worm press.

For cleaning of the channels 23, rinsing means 20, eg. spray nozzles areprovided. By means thereof a cleaning of the channels can take placeeven whilst in operation. Previously known designs of worm pressesfrequently had to be closed down and often even be taken apart forcleaning purposes.

In order to generate or regulate the pressure required in the terminalregion of the worm press for separating the liquid from the solidssuspension, appropriate flaps 21 are provided which can be regulated bymeans of hydraulic cylinders.

In FIG. 8 part of the terminal region of the worm press according to theinvention, is illustrated in longitudinal section. Partitions 19, 19'fixed to the solid cylinder wall 22 directed parallel to thelongitudinal axis and arranged in axial planes extend up to or nearly upto the drum wall 17 of the drum 13 which in that region has a conicaltaper. The drum wall 17, partitions 19 and solid cylindrical wall 22 or,where applicable, the cylindrical screen section 3' form channels 23from which the liquid is discharged with the separation of solid matterwhen passing in the downstream direction 8' through the cylindricalscreen section 3' from the worm press. Pressure can be applied to thefibrous suspension to be dewatered by means of the regulateable flap 21.

Finally FIG. 9 shows a cross sectional segment of the terminal region ofthe worm press including the individual channels 23 which are formed bythe drum wall 17, the partitions 19 and 19' and the solid cylindricalwall 22.

The embodiments illustrated in the Figures serve to elucidate theinvention. However, the invention is in no way limited to theseembodiments.

We claim:
 1. In an apparatus for separating liquid from fibrous pulpsuspensions comprising a solids retention means of multiple-layeredconstruction having liquid passages, wherein the layers are composed ofa screen (3) and a supporting body (4) for the screen, the improvementwhereinone layer, which faces the fibrous suspension, takes the form ofthe screen (3) with passages (7) which increase in cross-section in thedrainage direction of the liquid, another layer, which faces away fromthe fibrous suspension, takes the form of the supporting body (4) havingslot-shaped passages (5), and at least one free space for liquiddistribution is provided between the screen (3) and the supporting body(4).
 2. Apparatus according to claim 1, wherein the slot shaped passages(5) of the supporting body (4) are arranged parallel to one another,uniformly distributed over the surface of the supporting body. 3.Apparatus according to claim 2, wherein the cross section of each of theslot-shaped passages (5) of the supporting body (4) increases in thedownstream direction (8) of liquid drainage.
 4. Apparatus according toclaim 2, wherein the free space is provided in the form of channels (6and/or 6') between the screen (3) and the supporting body (4). 5.Apparatus according to claim 2, wherein the slot shaped passages arearranged in mutually staggered rows.
 6. Apparatus according to claim 1,wherein the cross section of each of the slot-shaped passages (5) of thesupporting body (4) increases in the downstream direction (8) of liquiddrainage.
 7. Apparatus according to claim 6, wherein the free space isprovided in the form of channels (6 and/or 6') between the screen (3)and the supporting body (4).
 8. Apparatus according to claim 1, whereinthe free space is provided in the form of channels (6 and/or 6') betweenthe screen (3) and the supporting body (4).
 9. Apparatus according toclaim 8, wherein the channels (6) are formed by spacers (6a) between thescreen (3) and the supporting body (4).
 10. Apparatus according to claim8, wherein the channels (6) are formed by grooves (6") provided in thescreen (3).
 11. Apparatus according to claim 8, wherein the channels (6)are arranged substantially transversely in relation to the slot-shapedpassages (5) of the supporting body (4).
 12. Apparatus according toclaim 8, wherein the channels (6') are provided in the form of groovesin the supporting body (4) extending to and as a continuation of thepassages (5) in the supporting body.
 13. The apparatus according toclaim 1, wherein the passages (7) are directed at right angles to thescreen surface.
 14. Apparatus according to claim 1, wherein bores areprovided in the screen (3) serving as said passages (7).
 15. Apparatusaccording to claim 1, wherein slots are provided in the screen (3)serving as said passages (7).
 16. Apparatus according to claim 15,wherein the slots (7) in the screen (3) are elongated at right angles tothe slot-shaped passages (5) through the supporting body (4). 17.Apparatus according to claim 1, wherein the slot-shaped passages (5) inthe supporting body (4) are provided at right angles to a surface of thesupporting body (4).
 18. Apparatus according to claim 1, wherein theinner cross section of the passages (7) in the screen (3) and of theslot-shaped passages (5) through the supporting body (4) are at leastpartly in alignment.
 19. Apparatus according to claim 1, wherein thesolids retention means takes the form of a hollow cylinder. 20.Apparatus according to claim 19, wherein the slot-shaped passages (5)through the supporting body (4) are normal to the surface of the hollowcylinder.
 21. Apparatus according to claim 19, wherein the slot-shapedpassages (5) in the supporting body (4) are oriented approximately inthe direction of the surface of the hollow cylinder.
 22. Apparatusaccording to claim 1, wherein the passages (7) through the screen (3)enter into grooves (6") on the side of the screen (3) facing thesupporting body (4).
 23. Apparatus according to claim 22, wherein saidgrooves extend transversely to the slot-shaped passages.
 24. Apparatusaccording to claim 1, wherein the solids retention means is of a planardesign.
 25. Apparatus according to claim 1, wherein the solids retentionmeans takes the form of a hollow frustoconical body.
 26. Apparatusaccording to claim 25, wherein the slot-shaped passages (5) through thesupporting body (4) are normal to the surface of the hollowfrustoconical body.
 27. Apparatus according to claim 25, wherein theslot-shaped passages (5) in the supporting body (4) are orientedapproximately in the direction of the surface of the hollowfrustoconical body.
 28. In a worm press for removing liquid from aliquid-solids suspension by conveying the suspension with a worm whichrotates about a longitudinal axis and is surrounded at least in part bya hollow wall defining solids retention means of multiple layeredconstruction having liquid passages, whereby liquid in said suspensionis drained in a direction through said passages as the suspension ispressed between the worm and the solids retention means, wherein saidsolids retention means comprises:a screen constituting one of saidlayers and defining screen passages, which extend outwardly from aninner side of the screen facing the suspension to an outer side facingaway from the suspension, the passages through the screen increasing incross-section in the drainage direction of the liquid; a supporting bodyconstituting another of said layers and having an inner surfacesupporting the outer side of the screen and slot-shaped passages fromthe inner surface to an outer surface, for the drainage of said liquid;and a free space between the screen and the supporting body, fordistributing the liquid from the passages in the screen to the passagesin the supporting body.
 29. Worm press according to claim 28, whereinthe slot shaped passages (5) of the supporting body (4) are arrangedparallel to one another, uniformly distributed through the supportingbody inner surface.
 30. Worm press according to claim 28, wherein thecross section of each of the slot-shaped passages (5) of the supportingbody (4) increases in the direction (8) of liquid drainage.
 31. Wormpress according to claim 28, wherein the free space is provided in theform of channels (6 and/or 6') between the screen (3) and the supportingbody (4).
 32. Worm press according to claim 31, wherein the channels (6)are formed by spacers (6a) between the screen (3) and the supportingbody (4).
 33. Worm press according to claim 31, wherein the channels (6)are formed by grooves (6") provided in the screen (3).
 34. Worm pressaccording to claim 31, wherein the channels (6) are arrangedsubstantially transversely in relation to the slot-shaped passages (5)of the supporting body (4).
 35. Worm press of claim 28, wherein boresare provided in the screen (3) serving as said screen passages (7). 36.Worm press of claim 28, wherein slots are provided in the screen (3)serving as said screen passages (7).
 37. Worm press of claim 28, whereinthe passages (7) through the screen (3) enter into grooves (6") on theouter side of the screen (3), facing the supporting body (4).
 38. Wormpress according to claim 28, wherein the worm of the worm press isprovided on the outer periphery of a hollow drum (13) and the hollowdrum in the terminal region of material conveyance in the worm pressincludes a cylindrical terminal screen section (3').
 39. Worm pressaccording to claim 38, wherein the terminal screen section has passagesfor draining liquid toward said longitudinal axis and the passages ofthe terminal screen section (3') have a cross section which increases inthe direction of drainage (8').
 40. Worm press according to claim 38,wherein the hollow drum (13) in its terminal region has a conical taper,the conical drum periphery (17) being surrounded by the cylindricalterminal screen (3') section followed by a solid cylindrical wall (22).41. Worm press according to claim 40, wherein planar partitions (19,19') are fixed in the solid cylinder wall (22), oriented transversely toand extending parallel with the longitudinal axis, and which jointlywith the terminal screen cylinder section (3') and with the drum wall(17) form channels (23) for the discharge of the liquid from theterminal region.
 42. Worm press according to claim 41, wherein at theend of the channels (23) an overflow (18) is provided for liquid. 43.Worm press according to claim 41, wherein at the end of the channels(23), rinsing means (20) are provided for cleaning the channels (23) ofentrained fibers.
 44. Worm press according to claim 40, wherein flatmeans (21) are provided for pressure regulation in the fibroussuspension in the terminal region outside of the terminal screencylinder section (3').